1. Field of the Invention
The invention relates to an analog-to-digital converter. Such converters are known and serve to convert the value of an analogue signal into a digital code.
2. Description of the Prior Art
An analog-to-digital converter is described by C. E. Woodward, K. H. Konkle and M. L. Naiman in an article entitled "A monolithic Voltage-Comparator Array for A/D Convertors" in "IEEE Journal of Solid-State Circuits", Vol. SC-10, No. 6, Dec. 1975, pages 392-396. This converter comprises a multitude of comparators whose noninverting inputs all receive a signal voltage and whose inverting inputs each time receive a different reference voltage, which reference voltages correspond to the input signal levels to be distinguished.
As generally only a very small voltage range is available and many different levels are to be distinguished, the comparators should have a fairly high voltage gain and a small offset. As appears from FIG. 3 of said article, this leads to fairly complex comparators, which have a comparatively high dissipation and which occupy much space in an integrated circuit.
It is an object of the invention to provide an analog-to-digital converter which can be realized very simply and which is suitable for processing signal currents.